Fix issues with printing of the system

[daniel-thom]

This also changes the return type of the function get_time_series_counts, which will break parent packages, such as PowerSystems.jl.

[codecov]

Codecov Report

Attention: 13 lines in your changes are missing coverage. Please review.

Comparison is base (2f8a2dc) 78.37% compared to head (600bfc2) 78.14%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #317      +/-   ##
==========================================
- Coverage   78.37%   78.14%   -0.23%     
==========================================
  Files          49       49              
  Lines        3967     3994      +27     
==========================================
+ Hits         3109     3121      +12     
- Misses        858      873      +15     

Flag	Coverage Δ
unittests	78.14% <77.96%> (-0.23%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/components.jl	90.78% <100.00%> (ø)
src/containers.jl	100.00% <100.00%> (ø)
src/supplemental_attributes.jl	78.04% <100.00%> (+3.65%)	⬆️
src/time_series_container.jl	77.19% <100.00%> (+0.40%)	⬆️
src/system_data.jl	88.79% <88.88%> (-0.19%)	⬇️
src/utils/print.jl	52.85% <64.28%> (+0.14%)	⬆️

... and 4 files with indirect coverage changes